A solution for dosimetr and quality assurance in IMRT and 一個解決的方案在調(diào)強放射治療的質(zhì)量保證和劑量學

1、a solution for dosimetry and quality assurance in imrt and hadrontherapy: the pixel ionization chamber.s. amerioa, s. bellettib, a. borianoc, r. ciriod, s. codaa, m. donettie,d,b. ghedib, a. lupariad, e. madonf, f. marchettod, u. nastasia,c. peronid,c.j. sanz freired,g, e. trevisiolf, a. urgesifa se

2、rvizio di fisica sanitaria, ospedale s. giovanni a.s., v. cavour 31, i-10123 torinob servizio di fisica sanitaria, spedali civili di brescia, p.le ospedale 1, i-25123 bresciac asp, v.le settimio severo 65, i-10133 torinod university and infn of torino, v. giuria 1, i-10125 torinoe tera foundation, v

3、. puccini 11, i-28100 novaraf oirm s. anna, v. baiardi 43, i-10126 torinof partially supported by iba, ion beam application, louven la-neuve, belgiumvilla olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics2introductionin intensity mo

4、dulated radiation therapy (imrt) techniques like step and shoot, sliding window, dynamic wedge and in hadrontherapy with scanning beam the delivered dose in the treated volume is not just function of the space but also of the time.an instrument useful in dose measurements has to be fast, reproducibl

5、e and able to measure in several points.we have developed, built and tested a fast ionization chamber segmented in pixels that measures the dose in a plane which can help the physicist in the dose measurements and in quality assurance.the outline of the talk is the followingdetector designread out e

6、lectronicsdata acquisitiontest performedresultsvilla olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics3detector designparallel plate ionization chamberanode segmented in 1024 square pixelspixel dimension = 7.5 x 7.5 mm2sensitive are

7、a = 24 x 24 cm2cathode made of aluminized mylar foiltotal dimension = 64 x 64 x 3 cm3front end electronics, placed around the chamber, perform the analog to digital conversionvilla olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics4d

8、etector designthin versionwhen used like monitor chamber the detector has to be thin to minimize the effects on the beam energy and shape.for this configuration, anode and cathode are glued to frames in order to assure the mechanical rigidity and the gap thickness .water equivalent thickness 1 mm.vi

9、lla olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics5detector designthick versionwhen used in plastic phantom the detector can be thick.with photon or electron beam air gap has to be minimized.anode and cathode are glued to a plast

10、ic slab, which is a grid of 1024 holes.each hole can be considered as an independent sensitive volume.villa olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics6read out electronicsthe read out electronics is housed next to the electro

11、des.we developed a very large scale integration (vlsi) chip.every chip has 64 channels that convert the collected charge in digital output.the name of the last version is tera05villa olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics

12、7read out electronicstera05 characteristics very large scale integration if conversion output qint 100 fccharge quantum800 fc fmax= 5 mhz imax= 4 a 64 channels 16 bit wide counters multiplexed digital output three-state output no dead time max read out = 10 mhzvilla olmo, como 15-19 october 2001done

13、ttito.infn.it7th international conference onadvanced technology and particle physics8read out electronicsrecycling integrator architecture.villa olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics9read out electronicsthe excellent lin

14、earity over a large range is due to recycling integrator architecture.qc = 600 fc10 pa i 2 alinearity better than 0.3 %qc = 100 fc20 pa i 0.6 alinearity better than 0.7 %villa olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics10read

15、out electronicscharge quantum have been measured over different chips in order to evaluate the spread of the value.results show an rms 1 %i = 49.96 na26 chipsvilla olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics11read out electron

16、icsi = 49.96 naqc = 600 fc24 c t 27 c1 month6 measurescharge quantum reproducibility has been measured.villa olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics12data acquisition connection by twisted pair flat cables (100 m max) max

17、rate transfer = 1 mhz = 2 mb/s read out transfer time = 1 ms pci daq card labview software cheap solution easy to handleslow data acquisitionvilla olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics13data acquisition connection by twi

18、sted pair flat cables (100 m max) max rate transfer = 10 mhz = 40 mb/s read out transfer time = 50 s read out cycle total time = 500 s (fifo operation + data transfer) real time operation system expensive solutionfast data acquisitionvilla olmo, como 15-19 october 2001donettito.infn.it7th internatio

19、nal conference onadvanced technology and particle physics14hadron beam testvoxelsgsi - darmstadt - germanybeam characteristics raster-scan delivery system 270 mev/u, c+6, 8.8 mm (fwhm) fast data acquisition system data acquisition synchronized with raster-scanaims spatial resolution homogeneity of r

20、esponsevilla olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics15hadron beam testspatial resolution 0.2 mmspatial resolutionpixel dimensions = 7.5 7.5 mm2beam dimension = 8.8 mm (fwhm)counts per voxel 103villa olmo, como 15-19 octobe

21、r 2001donettito.infn.it7th international conference onadvanced technology and particle physics16hadron beam testresponse homogeneitybefore calibration = 2.0 %after calibration = 1.1 %18 18 cm2 uniform fieldthe calibration accounts for the different gain of each channel (gas gap variations and electr

22、onics) villa olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics17photon beams. giovanni a.s. and s. anna hospitals torinoquality assuranceaims measurements reproducibility depth dose profile measurements and comparison to reference i

23、on chamber (farmer) results profile measurementsin such measurements there arent daq time constraints.anyway the system can measure the delivered dose in real time.villa olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics18photon beam

24、several measures have been performed to evaluate the reproducibility.after a pre-irradiation reproducibility is better than 1%100 mu per irradiationfield bigger than sensitive volumevilla olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle ph

25、ysics19photon beamdepth dose profiles have been measured for different photon energy.we use a farmer ion chamber in a plastic phantom to compare the results.an excellent agreement has been found for every photon energy.villa olmo, como 15-19 october 2001donettito.infn.it7th international conference

26、onadvanced technology and particle physics20photon beamprofile comparison with a water phantom have been performed.field 10 x 10 cm2depth 10 cmfield 20 x 20 cm2depth 10 cmvilla olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics21phot

27、on beamimrt measurementsdynamic wedge case: moving each side of the collimator with different speed one obtains a wedge shape of the dose at the end of the treatment one has to check the delivered dose in different pointsthe pixel ion chamber can measure precisely the 2d dose in 1024 points.villa olmo, como 15-19 october 2001donettito.infn.it7th international conference onadvanced technology and particle physics22photon beamdelivered dose in function